Power generation systems and methods for wheeled objects

ABSTRACT

A power generation system for wheeled objects comprises a generator mechanically coupled to one or more of the object&#39;s wheels to convert wheel rotational energy into electrical energy. The power generation system may comprise an electrical storage device configured to store the electrical power produced by the generator. Power from the generator and/or the electrical storage device can be used to provide power to other electrical systems in or on the object. In certain embodiments, the electrical storage device comprises a bank of high-capacity capacitors connected in series. Some embodiments use a control circuit, for example, to regulate the charging and discharging of the capacitor bank and to provide suitable voltages for other systems. The power generation system may be disposed within an object&#39;s wheel, such as a wheel of a shopping cart.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application Nos. 60/663,147, 60/663,327, and60/663,195, all filed on Mar. 18, 2005, the disclosures of which arehereby incorporated by reference. This application is being filedconcurrently with the following non-provisional applications, thedisclosures of which are additionally hereby incorporated by reference:U.S. patent application Ser. No. 11/277,027, filed Mar. 20, 2006, titledNAVIGATION SYSTEMS AND METHODS FOR WHEELED OBJECTS (hereinafter “theNavigation Patent Application”), and U.S. patent application Ser. No.11/277,016, filed, Mar. 20, 2006, titled TWO-WAY COMMUNICATION SYSTEMFOR TRACKING LOCATIONS AND STATUSES OF WHEELED VEHICLES (hereinafter“the Two-Way Communication Patent Application”).

BACKGROUND

1. Field

The present disclosure relates to electric power generation systems.More particularly the disclosure relates to systems and methods forstorage and management of electric power generated from the rotationalmotion of a wheeled object.

2. Description of the Related Art

Wheeled vehicles are used for many purposes, for example, to transportobjects or people. Often, vehicles include one or more on-board systems,devices, or components requiring a power source in order to operate. Forexample, the vehicle may include electronics and electrical circuitry,lighting systems, navigation systems, communication systems, etc. Inaddition, these systems may interact with other on-board electricalcomponents including, for example, computers, processors, input/outputdevices, transceivers, lights, brakes, and many other devices.

Power sources used to provide power to on-board systems in vehiclesinclude, for example, motors, engines, battery systems, solar cells, andthe like. However, such power sources have disadvantages. For example,motors and engines are often heavy, noisy, and may require refuelingfrom an exogenous source. Motors and engines are often not suitable forindoor use. Battery systems can discharge, which requires the battery tobe replaced or recharged. Solar cells may provide insufficient powerindoors or at night. Moreover, many vehicles such as, for example, apush-cart or a pull-cart, are propelled by a person and using the abovepower sources disadvantageously adds additional weight and takes upusable space on the vehicle.

SUMMARY

A power generation system for wheeled objects comprises a generatormechanically coupled to one or more of the object's wheels to convertwheel rotational energy into electrical energy. The power generationsystem may comprise an electrical storage device configured to store theelectrical power produced by the generator. Power from the generatorand/or the electrical storage device can be used to provide power toother electrical systems in or on the object. In certain preferredembodiments, the electrical storage device comprises a bank ofhigh-capacity capacitors connected in series. Some embodiments use acontrol circuit, for example, to regulate the charging and dischargingof the capacitor bank and to provide suitable voltages for othersystems. In some embodiments, the power generation system is configuredto be disposed within the object's wheel.

In a preferred embodiment, the rotational motion of the wheel iscommunicated to an AC generator disposed (in whole or in part) in thewheel. In certain embodiments, the capacitor bank comprises one or morehigh energy density ultracapacitors, some or all of which may havecapacitances above 1 Farad (F). Some or all of the capacitor bank may bedisposed in the wheel. In some embodiments suitable for use on carts(e.g., shopping carts), the generator is configured to charge thecapacitor bank to a suitable working voltage (e.g., from about 2 V toabout 5 V) after the wheel has traveled a distance in the range fromabout 10 m to about 30 m.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention(s) will now be described withreference to the following drawings illustrating certain preferredembodiments.

FIG. 1 is a perspective view of a retail store and associated property,illustrating shopping carts that use a wheel power generation system toprovide electrical power to other systems disposed on the carts.

FIG. 2A is a plan-view of an embodiment of a wheel and wheel assemblythat can be used on an object such as a cart.

FIG. 2B is an exploded view of the wheel assembly shown in FIG. 2A.

FIG. 3A is a perspective front view of the hub of the wheel with thecover and control circuitry removed.

FIG. 3B is a perspective front view of the hub of the wheel shown inFIG. 3A with the control circuitry in place.

FIG. 3C is a perspective rear view of the hub of the wheel.

FIG. 3D is a perspective view of an embodiment of a generator sized tofit within the hub of the wheel of FIGS. 3A-3C.

FIG. 3E is a cross-section view of another embodiment of a wheelcomprising a power system and a brake system.

FIG. 4A is a cross-section view of an embodiment of an electricallysplit axle that can be used to route power from the wheel to off-wheelelectrical systems.

FIG. 4B is a cross-section view showing a portion of the wheel assemblyconnected to the electrically split axle

FIG. 5A is a circuit diagram of an embodiment of a control circuitconfigured to regulate the charging and discharging of a capacitor bankand to provide suitable voltages for other electronic devices.

FIG. 5B is a circuit diagram of another embodiment of a control circuitincluding an optional backup power source.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

I. Overview

Various embodiments of the present invention provide systems and methodsfor power generation, storage, and management for a wheeled object. Incertain embodiments, the wheeled object has one, two, three, four, ormore wheels. The wheeled object includes, but is not limited to, avehicle, a cart, a carrier, a transport, a gurney, a carriage, a wagon,a stroller, a wheelchair, a hospital bed, a pharmacy cart, a walker,carts used for medical and other equipment, or any other suitableconveyance. In certain preferred embodiments, the wheeled object is ashopping cart, a warehouse cart, an industrial cart, a luggage cart, ora baggage cart. In some embodiments, the wheeled object isself-propelled, while in other embodiments, the wheeled object requiresan outside source, such as a person, to move the object. Accordingly,the various inventive features described herein are applicable to a widerange of different types of wheeled objects and vehicles.

As the wheeled object moves, its wheels rotate. As is well known, arotating wheel contains mechanical energy in the form of rotationalenergy. Accordingly, this disclosure advantageously provides embodimentsof systems and methods that are configured to convert a portion of thewheel's rotational energy into electrical energy that can be used topower other systems, components, and devices on the object. In addition,certain embodiments beneficially provide systems and methods forelectrical power storage and management.

In some embodiments, a portion of the rotational energy of the wheel isconverted into electrical power by a generator. As used herein, the term“generator” is a broad term, and is used in its ordinary sense, andincludes without limitation, unless explicitly stated, an apparatus thatconverts mechanical energy into electromagnetic energy. A generatorincludes, but is not limited to, a dynamo or an alternator. A generatormay produce a direct current (DC) and/or an alternating current (AC).Mechanical energy includes, but is not limited to, kinetic energy, andin some embodiments, rotational kinetic energy. In certain preferredembodiments, a generator produces electrical power from a portion of themechanical energy of one or more rotating wheels.

As is well known, generators typically produce electricity throughrelative motion between one or more magnets and one or more coilscomprising wire windings. According to Faraday's law, the relativemotion between a magnet and a coil induces electricity (e.g., voltageand/or current). For example, embodiments of generators often comprise arotating portion (a rotor) and a stationary portion (a stator). Therotor is configured so that a source of mechanical energy causes therotor to move (e.g., rotate) relative to the stator. The motion of oneor more magnets disposed on the rotor induces electrical power in thewindings disposed on the stator. In other embodiments, the magnets aredisposed on the stator, and the coils are disposed on the rotor. Thegenerator may be configured so that the rotor turns within the stator,or the stator may be disposed within the rotor. The magnets can bepermanent magnets and/or electromagnets. Many generator variations arepossible, as is well known in the electrical arts.

In embodiments adapted for use in wheeled objects, one or moregenerators are disposed in or on the object and mechanically coupled toone or more wheels so that electrical power is generated when the wheelsturn. In certain preferred embodiments, the generator is sized andshaped so that portions of it can fit within the wheel as furtherdescribed herein. Many types of commercially available generators can beused with the systems and methods disclosed herein.

The generator can be configured to provide an AC current and/or a DCcurrent, in various embodiments. For example, some embodiments of thepower system include one or more rectification circuits to convert an ACcurrent into a DC current usable by other systems. In other embodiments,the generator is configured to produce a DC current by using, forexample, a commutator, brushes, and/or slip rings

In certain embodiments, the generator is electrically coupled to anelectrical energy storage device, which stores the electrical energy foruse when the generator is not producing electricity. The electricalstorage device can comprise one or more capacitors, rechargeablebatteries, or other suitable devices for storing electrical energy. Insome embodiments, the electrical storage device comprises one or morecapacitors having a high capacitance, a high energy density, and/or ahigh power density. Such high-capacity capacitors are commonly known asultracapacitors (or supercapacitors) and can store relatively largeamounts of electrical energy. As used herein, the term “ultracapacitor”is a broad term, and is used in its ordinary sense, and includes withoutlimitation, unless explicitly stated, any capacitor having a highcapacitance, high energy density, and/or high power density.Ultracapacitors include capacitors having capacitances greater thanabout 0.1 F, and in particular, greater than about 1 F. Ultracapacitorsinclude capacitors having an energy density above about 0.1Watt-hour/kg, and/or power densities above about 5 Watts/kg. Anultracapacitor includes, for example, a supercapacitor, an electricdouble layer capacitor (EDLC), and an aerogel capacitor.

Other systems disposed in or on the object can be configured to use theelectrical energy generated by the generator and stored in theelectrical storage device during times when the object's wheels are notrotating (e.g., when the generator is not providing power). In someembodiments, these systems are disposed substantially within the wheel,and/or they may be distributed throughout the object. Electrical powercan be provided by disposing wired connections between these systems andthe generator and/or the electrical storage device. In some embodiments,the electrical storage device comprises a backup power system such as,for example, a backup battery system (which may comprise disposableand/or rechargeable batteries), from which power can be drawn if theultracapacitors discharge.

Embodiments of the power system additionally comprise control circuitrythat provides rapid and efficient charging of the energy storage device,reduces the discharge rate of the storage device, and provides one ormore voltages suitable for operating other systems, among otherfunctions.

In some preferred embodiments, the power system is disposed within awheel of the object. However, in other embodiments, portions of thepower system are disposed elsewhere in the object, for example, in awheel assembly attaching the wheel to the object (e.g., a fork or acaster), or in a portion of the object's frame or handlebars, or inother suitable locations. The power system can be configured to supplypower to systems disposed in a wheel (including, but not limited to, thewheel comprising the generator) or to systems disposed elsewhere in theobject (e.g., a display mounted to the handlebars). It is recognizedthat that the power system can be configured in a wide variety of waysand electrically coupled to many types of systems.

II. Example Operating Scenario

The power system disclosed herein can be used in any wheeled device andcan be configured to provide power to any type of system or systems onthe object. For purposes of illustration, an example scenario will nowbe discussed that illustrates some of the features and advantages of thepower system. This example scenario is intended to facilitateunderstanding of certain embodiments of the power system and uses of thepower system and is not intended to limit the scope of the principlesdisclosed herein.

In the sample scenario shown in FIG. 1, a retail store 110 implements aloss prevention system to reduce the theft of shopping carts 122 from atracking area 114. The tracking area 114 may comprise, for example, aportion of a parking lot adjacent to the store 110. An objective of theloss prevention system is to prevent, or at least reduce, theunauthorized transport of carts 122 across a boundary (or perimeter) 118of the lot 114. In one embodiment of the loss prevention system, eachcart 122 may include an anti-theft system comprising, for example, analarm or a mechanism to inhibit motion of the cart 122.

Cart motion can be inhibited, for example, by providing at least onewheel of the cart 122 with a brake mechanism configured to lock thewheel. Cart motion can be inhibited in other ways, as is known in theart. For example, the wheel braking mechanism described herein can bereplaced with another type of electromechanical mechanism for inhibitingthe motion of the cart, including mechanisms that cause one or more ofthe wheels of the cart 122 to be lifted off the ground. In someembodiments, the brake mechanism comprises a motor that drives anactuator that can engage an inner surface of the wheel so as to inhibitthe motion of the wheel. In certain embodiments, the brake mechanism hasan unlocked state in which the wheel can substantially freely rotate anda locked state in which the wheel's rotation is substantially impeded.In other embodiments, the brake mechanism is progressive, wherein theactuator can apply differing amounts of braking force to the wheel. Abrake mechanism suitable for use with wheeled devices such as shoppingcarts is disclosed in U.S. Patent No. 6,945,362, issued Sep. 20, 2005,titled “ANTI-THEFT VEHICLE SYSTEM,” which is hereby incorporated byreference herein in its entirety.

To prevent loss, if the cart 122 is moved across the lot boundary 118,the anti-theft system is activated (e.g., the alarm or the brake istriggered). In some loss prevention systems, the anti-theft system isactivated if the cart 122 detects a signal from an external transmitterpositioned near the lot boundary 118. For example, the signal may be aVLF signal transmitted from a wire buried at the boundary 118, such asdescribed in U.S. Pat. No. 6,127,927, issued Oct. 3, 2000, titled“ANTI-THEFT VEHICLE SYSTEM,” which is hereby incorporated by referenceherein in its entirety.

In some embodiments, a navigation system is used to determine theposition of the cart 122 within the tracking area 114. The navigationsystem can be disposed on or in the cart 122 or in a central controller138. If the navigation system determines the position of the cart 122 tobe outside the lot boundary 118, the anti-theft system can be activated.In one embodiment, the navigation system begins to monitor cart positionwhen the cart 122 leaves a store exit 126. The initial cart position isset to be the position of the exit, and the navigation system updatesthe position of the cart 122 by a dead reckoning algorithm. The deadreckoning algorithm uses object speed, heading, distance traveled, andelapsed time to estimate the position of the cart. Accordingly, invarious embodiments, the cart 122 includes heading sensors, motionsensors, and processors. In one embodiment, the object's heading ismeasured with respect to the Earth's magnetic field, and the cart 122includes magnetic field sensors to determine, e.g., the object'sdirection of travel with respect to geomagnetic North. To determine thecart's speed or distance traveled, one or more wheels may includerotation sensors including, for example, mechanical, optical, ormagnetic rotary encoders.

In some embodiments, the navigation system is provided with the positionof the lot boundary 118, for example, as a set of coordinates. Bycomparing the present position of the cart 122 with the position of theboundary 118, the system can determine whether the cart 122 is withinthe lot 114. If the navigation system determines the cart 122 is movingacross the lot boundary 118, the navigation system can activate thecart's anti-theft system. In a preferred embodiment, the navigationsystem is sized so as to fit within a wheel of the cart 122. In otherembodiments, portions of the navigation system can be disposed in awheel, while other portions can be disposed elsewhere in the cart 122(e.g., in handlebars or the frame). A navigation system suitable for usewith a wheeled object, such as a shopping cart, is disclosed in theNavigation Patent Application.

In other embodiments, the navigation system communicates the position ofthe cart 122, or other information, to a central processor or thecentral controller 138, which determines whether the cart 122 has exitedthe lot 114 and whether the anti-theft system should be activated. Incertain preferred embodiments, the cart 122 includes a two-waycommunication system that enables suitable information to becommunicated between the cart 122 and the central controller 138 (orother suitable transceivers). The communication system may include oneor more antennas, transmitters, receivers, transceivers, signalgenerators, or other components. A two-way communication system suitablefor use with the navigation system is disclosed the Two-WayCommunication Patent Application.

Other devices can be advantageously used by the retail store 110 in thissample scenario. For example, one or more markers 130 a-130 c can bedisposed at various locations throughout the lot 114 to serve asreference locations, landmarks, or beacons. The markers 130 a-130 c canmark or otherwise indicate the position of, for example, store exits 126(e.g., marker 130 a), the perimeter of the lot 114 (e.g., markers 130c), and/or other suitable reference locations (e.g., marker 130 b). Invarious embodiments, the markers 130 a-130 c communicate information tothe navigation system by, for example, magnetic or electromagneticmethods. The navigation system may use information communicated from amarker 130 a-130 c to reduce accumulated navigational errors, todetermine that a lot boundary 118 is nearby, or for other purposes. Insome embodiments, one or more markers (e.g., the markers 130 c) may bedisposed near locations of entrances/exits 142 to the parking lot 114.

In one embodiment, one or more transmitters 134 are disposed throughoutthe lot 114 and are configured to transmit information to the navigationsystem in the carts 122. The transmitters 134, in an embodiment, alsoreceive information (e.g., they are transceivers). In variousembodiments, the markers 130 a-130 c (and/or the transmitters 134)communicate with the carts 122 via one-way (to or from the cart) ortwo-way (to and from the cart) communication protocols. For example, themarkers 130 and/or transmitters 134 may be configured to useelectromagnetic signals to communicate with the cart 122. These signalsmay include magnetic signals and/or RF or VLF signals. As used herein,RF signals comprise electromagnetic signals having frequencies belowabout 300 GHz, and VLF (“very low frequency”) signals comprise RFsignals having frequencies below about 20 kHz.

In other embodiments, one or more access points (AP) 136 are used tocreate two-way communication links with the carts 122. In FIG. 1, theaccess point 136 is shown positioned above the exit 126 of the store110, which beneficially allows the AP to communicate with carts 122located throughout the parking lot 114. In other implementations, morethan one AP can be used, and the AP's can be located throughout thetracking area. Access points 136 can communicate with a transceiver inthe cart 122 (e.g., an RF transceiver), which is connected to thenavigation system (and/or other components) for purposes of retrieving,exchanging, and/or generating cart status information, includinginformation indicative or reflective of cart position. The types of cartstatus information that may be retrieved and monitored include, forexample, whether an anti-theft system has been activated (e.g., whethera wheel brake is locked or unlocked); whether the cart 122 is moving andin which direction; the wheel's average speed; whether the cart 122 hasdetected a particular type of location-dependent signal such as a VLF,EAS, RF, or magnetic signal (discussed below); whether the cart isskidding; the cart's power level; and the number of lock/unlock cyclesexperienced by the cart per unit time. The access points 136 can alsoexchange information with the navigation system related to the positionof the perimeter 118. In some embodiments, the access points 136 use areceived signal strength indicator (RSSI) to measure the strength of thesignal received from the cart 122 to assist in determining the distanceto the cart 122 and whether the cart is moving toward or away from thestore 110. Further details on the implementation and use of a set ofwireless access points (AP) is disclosed in the Two-Way CommunicationPatent Application.

The navigation system may be used by the store 110 for purposesadditional to or different from loss prevention. In some embodiments,the retail store 110 may wish to gather information related to thepositions and paths taken by the carts 122. For example, the retailstore may wish to determine where in the lot 114 that customers leavecarts 122 so as to improve cart retrieval operations. In otherembodiments, the navigation system can communicate with other devicessuch as, for example, a mechanized cart retrieval unit.

Although the sample scenario has been described with reference to a lossprevention system for shopping carts 122 in a parking lot 114 outside aretail store 110, in some embodiments, the navigation system isconfigured to determine the position of a cart 122 within the store 110.For example, the system may be used to determine whether a cart 122 haspassed through a checkout lane or whether the cart 122 has passedthrough selected aisles. In addition, the navigation system may be usedto track cart positions so as to gather information related to theclustering or queuing of carts at certain locations inside or outsidethe store 110. Moreover, other systems may be disposed on the cart 122including, for example, an input/output device such as a display,monitor, touchscreen, keyboard, or keypad and/or a lighting system(including, e.g., headlights, taillights, turn signals, and/or indicatorlights). Further details of a handle-mounted display system that can beelectrically powered by the power system disclosed herein are discussedin the Two-Way Communication Patent Application.

Accordingly, the cart 122 can include a wide variety of systems, witheach system having its own power needs. For example, a motor in a brakesystem may require relatively high voltage, current, and power tooperate, while a microcontroller system may require lower operatingvoltage and power. Some systems require a continuous supply of power(e.g., a navigation system, a display, or a light), while other systemsuse power intermittently (e.g., when a wheel brake is activated).Therefore, it is beneficial to dispose on the cart 122 a power systemthat can generate and store sufficient power for each of these systems.

In some embodiments, the power generation system is disposed within andprovides power to one or more systems also located in the wheel. Forexample, in one preferred embodiment, the power generation system isdisposed within a wheel and is used to power a brake system alsodisposed in the wheel. However, this is not a requirement, and in otherembodiments, the power system is connected, for example, by electricalwires, to systems disposed elsewhere (e.g., in or on the handlebars orframe of a cart). For example, in various embodiments, the wheel powersystem can be used to power a display attached to the cart's handlebars,one or more lights attached to the frame, a communications systemdisposed in the cart's frame, and an anti-theft system (including, e.g.,an alarm and/or a wheel brake, which may be disposed in a differentwheel than the power system). In another preferred embodiment, the powersystem is used to power one or more transceivers (e.g., RF or VLFtransceivers) disposed in the cart and used to communicate with othertransmitters 134 or access points 136. Many variations are possible, anda skilled artisan will recognize the versatility of uses for the powersystem disclosed herein.

Embodiments of the above-mentioned systems may be used in otherenvironments and contexts such as, for example, a warehouse, anindustrial plant, an office building, a hospital, an airport, or otherfacility. Accordingly, the power systems and methods disclosed hereincan be used in many different types of facilities and in many types ofwheeled objects. Many variations of the sample scenario discussed aboveare possible without departing from the scope of the principlesdisclosed herein.

III. Wheel with Power Generation System

FIG. 2 is a plan-view of an embodiment of a wheel assembly 210comprising a wheel 212 and a caster 240 (also known as a “fork” or a“yoke”). The wheel assembly 210 is adapted to be attached to an object,such as a cart, by being screwed in to the object. The wheel assembly210 can be used to replace one (or more) of the wheels on the object.For example, the wheel assembly 210 can replace a standard-sized front(and/or rear) wheel on a shopping cart. In certain embodiments, thewheel 212 has a diameter of about five inches, although the wheel 212can be larger or smaller in other embodiments. The wheel 212 includes atire 213 that is circumferentially disposed about a hub 218 (see FIGS.3A-3C). The hub 218 rotates with the tire 213. The hub 218 can have acover 221 that protects components disposed within the hub 218 fromenvironmental conditions In addition, the cover 221 prevents internalcomponents from being seen and tampered with by users of the object. Thehub 218 (and the cover 221) can be fabricated from rigid, lightweightmaterials including plastics such as nylon or acrylonitrile butadienestyrene (ABS).

FIG. 2B is an exploded view of the wheel assembly 210. The wheel 212 isdisposed between end portions 242 of the caster 240. The end portions242 fit into “U”-shaped retaining clips 225. A bolt 228 passes throughthe retaining clips 225, the end portions 242, and a hollow axle 234 inthe center of the hub 218. A nut 232 is tightened to secure the wheel212 to the caster 240. The axle 234 has flat portions 235 that engageshaped holes 237 in the retaining clips 225. The axle 234 is preventedfrom rotating by the interference fit between the “U”-shaped sides ofthe retaining clips 225 and the end portions 242 of the caster 240.Internal components disposed within the hub 218 can be prevented fromrotating by attaching them to the non-rotating axle 234. The wheel 212can be configured to contain some or all portions of other suitablesystems including, for example, a power system, a navigation system, ananti-theft system, a brake system, and/or a two-way communicationsystem.

FIGS. 3A-3C schematically illustrate an embodiment of the wheel 212 thatcomprises a power system and a brake system. FIGS. 3A and 3B are frontperspective views showing the arrangement in the hub 218 of internalcomponents of the power system and the locking system. For clarity ofpresentation, the tire 213, which surrounds the circumference of the hub218, and the hub's cover 221 are not shown in FIGS. 3A-3B. The internalcomponents are prevented from rotating by attaching them to a chassis312, which is rigidly attached to the non-rotating axle 234. In someembodiments, the chassis 312 is made from an electrically insulatingmaterial, for example, a plastic material such as nylon or ABS.

The power system comprises a generator 313, an electrical storage device330, and control electronics. The generator 313 comprises a rotor 318housed within a stator 322 and free to rotate therein. The generator 313will be further described with reference to FIG. 3D. The power systemcontrol electronics can be fabricated on a printed circuit boardassembly 334 (PCBA). The PCBA 334 is not shown in FIG. 3A in order toillustrate the electrical storage device 330 disposed within a cavity333 in the chassis 312. FIG. 3B shows the PCBA 334 in place over thecavity 333.

The brake system comprises a brake motor 354, a drive mechanism 358, anda brake band 362. The brake system further comprises control electronicsfabricated on the PCBA 334. In other embodiments, separate PCBA's can beused for the brake and the power system electronics. The brake motor 354engages the drive mechanism 358 (e.g., a set of gears) to drive thebrake band 362 into and out of contact with an inner surface 340 of therotating hub 218. The brake motor 354 generally is a DC servo or steppermotor operable in a forward and a reverse direction. In someembodiments, the DC motor 354 has an operating voltage of about 5 V.

The brake system is operable between an unlocked and a locked state. Inthe unlocked state, the brake band 362 does not contact the hub 218, andthe wheel is substantially free to rotate. In the locked state, thebrake band 362 expands outward and contacts the hub 218. The innersurface 340 may include a series of protrusions 342 that engage notchesin the brake band 362 to prevent rotation of the wheel 212. In otherembodiments, different brake systems can be used such as, for example,the brake mechanisms disclosed in U.S. Pat. No. 5,598,144, issued onJan. 28, 1997, entitled “ANTI-THEFT VEHICLE SYSTEM,” or U.S. Pat. No.6,945,362, issued Sep. 20, 2005, entitled “ANTI-THEFT VEHICLE SYSTEM,”each of which is hereby incorporated by reference herein in itsentirety. Moreover, in other embodiments a progressive brake mechanism,which provides a variable amount of braking force to the wheel 212, canbe used.

FIG. 3C is a rear perspective view of the hub 218 that illustrates amechanism that transmits the rotational motion of the wheel 212 to thegenerator 313. A drive gear ring 314 is attached to and rotates with thehub 218. The drive gear ring 314 engages a pinion gear 326 that isattached to the rotor 318 (see also FIG. 3D). Rotation of the wheel 212causes the rotor 318 to rotate within the generator 313. The gear ratiobetween the drive gear ring 314 and the pinion gear 326 can be used toprovide a suitable rotation rate for the rotor 318. In some embodiments,the gear ratio is 10:1 or 15:1, although other gear ratios can be used.

In some embodiments, the drive gear ring 314 is formed as a moldedfeature in a cover to the hub 218 or in the hub 218 itself. Throughnormal use, the drive gear ring 314 may become slightly noncircular or“out-of-round” and may not fully engage the pinion gear 326, which canlead to gear wear. Accordingly, some embodiments beneficially usesecondary gearing that “floats” on the drive gear 314 and maintainssolid contact with the pinion gear 326 to reduce gear wear even if thedrive gear ring 314 becomes slightly noncircular.

a. Generator

FIG. 3D is a perspective view of an embodiment of the generator 313. Inthis embodiment, the stator 322 comprises a number of posts or legs 323arranged in a generally cylindrical, cage-like configuration around therotor 318. The rotor 318 is free to rotate within the stator 322 andcomprises one or more generally cylindrically-shaped, magnetized disksThe legs 323 of the stator 322 comprise the windings of the generator313. Rotation of the rotor 318 within the stator 322 induces electriccurrent to flow within the windings. The electric current is provided toother components via wires 325. For example, the wires 325 may connectthe generator to the electric storage device 330 and the PCBA 334.

The generator 313 produces an AC current. In this embodiment, thegenerator 313 is a 24-pole generator that produces 12 cycles of electricpower for each rotation of the rotor 318. In other embodiments, adifferent number of poles can be used. In other embodiments, thegenerator 313 can include brushes, slip rings, and/or commutators toprovide a DC current. However, brushes, slip rings, and commutators aresubject to frictional wear and impairment and require periodicadjustment or replacement. Embodiments not using these componentsadvantageously reduce the need for generator maintenance and areparticularly beneficial in environments (such as a retail store'soutdoor parking lot) where the generator is subject to dirty andshock-prone conditions.

Generally, the power output of the generator 313 is roughly linearlyproportional to the rotor's rotational rate. The gear ratio between thedrive gear ring 314 and the pinion gear 326 can be selected so that thegenerator 313 produces a suitable amount of power for wheel speedstypically encountered in an implementation. For example, inan-embodiment suitable for use in a retail store 110 environment (FIG.1), the shopping cart 122 is generally moved at normal walking speeds inthe range from about 1 ft/s to about 5 ft/s. The outer diameter 214 of astandard shopping cart wheel 212 is about 5 inches. Accordingly, atnormal walking speeds the wheel 212 rotates in the range from about 50revolutions per minute (rpm) to about 250 rpm. If a gear ratio of 10:1is used, and the generator 313 has 24 poles, then one wheel rotationproduces 120 cycles of electrical power. Such an embodiment of thegenerator 313 provides electrical power in the range from about 80 mW toabout 400 mW. An embodiment of the wheel 212 having a gear ratio of 15:1provides about 120 mW to about 600 mW of electrical power.

In the generator embodiment shown in FIG. 3D, the rotor 318 comprises apermanent magnet that rotates within the stator 322. In otherembodiments, the rotor 318 and/or the stator 322 may include one or moreelectromagnets, which allows for variable power output from thegenerator 313. In such embodiments, the power output can be adjusted thepower system control circuit based on, for example, charging needs,instantaneous power consumption, the electrical load fed by thegenerator 313, etc.

b. Electrical Storage Device

The power system includes the electrical storage device 330, which incertain embodiments, comprises one or more capacitors. For example, FIG.3A shows an embodiment utilizing two capacitors 330. In certainpreferred embodiments, capacitors having a high capacitance are selectedbecause of their ability to store relatively large amounts of electricalenergy. For example, in certain embodiments, the electrical storagedevice 330 comprises one or more ultracapacitors. Because someultracapacitors have voltage limits (e.g., about 2.5 V) that are lessthan the voltage needed to operate certain systems on the object (e.g.,a braking system), various embodiments use a bank of capacitorsconnected in series to provide a higher working voltage. In certain suchembodiments, the capacitor bank may comprise two, three, four, five, ormore capacitors. In other embodiments, the capacitor bank is connectedin parallel or in series/parallel combinations.

As is well known, any real capacitor has an internal electricalresistance known as the equivalent series resistance (ESR). It ispreferable, although not required, for capacitors used in the electricstorage device 330 to have a low equivalent series resistance (ESR) soas to provide a high electric power discharge rate. In some embodiments,the ESR of the capacitors is less than about 1 Ohm.

In some embodiments, the electric storage device 330 comprises a seriescapacitor bank comprising two Cooper-Bussmann PowerStor® AerogelCapacitors B1010-2R5155 (Cooper Electronic Technologies, Boynton Beach,Fla.), each rated at a capacitance of 1.5 F and a working voltage of 2.5V. This device provides a maximum working voltage of about 5 V. Inanother embodiment, the capacitor bank comprises three Cooper BussmannPowerStor B0830-2R5475 1.6 F EDLC ultracapacitors connected in series toproduce a 7.5 V maximum working voltage and a nominal ESR of about 0.45Ohms. In different embodiments, different numbers of ultracapacitors canbe used. Other suitable ultracapacitors include: a Maxwell Boostcap®PC10 EDLC (Maxwell Technologies, San Diego, Calif.); a NesscapESHSR-0003C0-002R7 EDLC (Nesscap Corp., Kyongg-Do, Korea); an EppscoreAC1020 ultracapacitor (Eppscore Corp., Seoul, Korea); and an EPCOSB49100A1104M00 ultracapacitor (EPCOS AG, Munich, Germany).

The electric storage device 330 may comprise additional electroniccomponents, including, for example, capacitors, diodes, resistors,inductors, transistors, regulators, controllers, batteries, and anyother suitable electronic device. In some embodiments, the additionalelectronic components assist in storing and discharging electricalenergy and in directing the electrical energy to suitable systems.Although the embodiment of the storage device 330 shown in FIG. 3Acomprises two ultracapacitors, this is not a limitation. For example, insome embodiments, the electric storage device 330 includes one or morebatteries (disposable and/or rechargeable), one or more lower capacitycapacitors, and/or one or more fuel cells. It is contemplated that theelectric storage device 330 may use any type of device, component, orsystem configured to store electromagnetic energy, including those nowexisting and those to be developed in the future.

In some embodiments, the electric storage device 330 further comprises abackup battery that can be used to power various on-board systems if thecapacitor bank discharges below a minimum operating voltage suitable forthe on-board systems. The backup battery may comprise disposable and/orrechargeable batteries. In certain embodiments, electrical power fromthe generator 313 is used to charge the backup battery.

In another embodiment, the electrical storage device 330 comprises oneor more Lithium Vanadium Pentoxide rechargeable batteries (e.g.,Panasonic VL3032 100 mAh cells). Because the self-discharge rate ofLithium Vanadium Pentoxide batteries (about 2% per year at roomtemperature) is significantly lower than the self-discharge rate of manycommercially available EDLC's, this embodiment may beneficially be usedin implementations that have low power needs and long term energystorage needs after the generator stops producing electricity (e.g.,when the wheel stops rotating).

Lithium Vanadium Pentoxide batteries have different electricalcharacteristics compared to ultracapacitors. For example, they havelower energy capacity (e.g. for a Panasonic VL3032, 100 mAh*2.7 V=0.27Joules compared to many Joules for most commercially availableultracapacitors), lower current, and relatively slow charging rate (4mA). Accordingly, implementations using Lithium Vanadium Pentoxidebatteries rather than ultracapacitors will generally also have lowenergy capacity, current, and charging rate requirements.

In another embodiment, the electrical storage device 330 comprises twoor more devices utilizing different energy storage technologies, e.g.,an ultracapacitor and a Lithium Vanadium Pentoxide battery. Thisembodiment may advantageously be used in an implementation where thereis a need for significant current (e.g. greater than about 200 μA) in atime and motion profile which meets the ultracapacitor discharge profile(e.g., no significant current is needed after a few days withoutcharging), but where some smaller energy storage is needed on a muchlonger time scale (e.g., for weeks, months, or years after the wheelstops rotating).

In other embodiments, the electrical storage device 330 may comprisebatteries having other types of rechargeable battery chemistry (e.g.,NiMH or lithium ion). For example, the volumetric energy density of someNiMH batteries is higher than that of some ultracapacitors, and the selfdischarge rate is somewhat lower, which may make them suitable for someimplementations. However, for most implementations, the rapid charging,high cycle count, and high available discharge current ofultracapacitors makes them a preferred embodiment for the electricalstorage device.

c. Alternative Embodiments

The components of the power system and the brake system can beconfigured differently than shown in FIGS. 3A-3C. For example, FIG. 3Eis a plan-view that schematically illustrates an alternative arrangementof the above-mentioned components within the wheel 212.

In the embodiments illustrated in FIGS. 3A-3E, all the components of thepower and braking systems are contained within the wheel. However, inother embodiments, some or all of these components can be disposedoutside the wheel 212. For example, some or all of the components can bedisposed in an enclosed plastic housing that forms part of the wheelassembly or caster. In embodiments suitable for carts, some or all ofthe components can be disposed in or on the frame or the handlebars ofthe cart. In some embodiments, the power system and the brake system aredisposed in different locations in the object. For example, the brakesystem can be disposed in a first wheel and the power system can bedisposed in a second wheel. As will be recognized, there are manypossible variations for the configuration and layout of the power systemand braking system.

d. Powering Off-Wheel Systems

The power system can provide power to systems and components both insidethe wheel (“in-wheel” systems) and outside the wheel (“off-wheel”systems). FIGS. 3A-3E illustrate embodiments wherein the power systemprovides power to an in-wheel system (e.g., the brake system).

However, in other embodiments, systems such as a navigation system or atwo-way communications system may be disposed in other places on theobject (including in a different wheel than the power system). Forexample, in some preferred embodiments, a display, monitor, or othersuitable input/output device (e.g., audio speakers and/or a microphone)is mounted to a portion of the object such as, for example, a handle ona shopping cart. The display may include a display screen, such as atouch screen, that is viewable by a person pushing the object. Thedisplay can be used to display information received from other systemson the object (e.g., a navigation system, a two-way communicationsystem, an anti-theft system, etc.). For example, the display may show agraphic illustrating the position of the object within a facility. Thedisplay may be connected to other controllers, processors, and/ortransceivers and configured to output additional information. Inembodiments suitable for a retail store, the display may have a cardreader or wand that enables customer to swipe a customer loyalty card oranother type of card that identifies the customer. In these embodiments,a transceiver on the object may be configured to convey the customeridentifier (as well as position information from a navigation system) toa remote transceiver (or an access point) such that this identifier (andposition information) can be associated with other information receivedfrom the cart during the customer's shopping session. Furtherinformation related to tracking the locations and monitoring the statusof objects (such as shopping carts) is disclosed in the Two-WayCommunication Patent Application and further information related todetermining the position of an object is disclosed in the NavigationPatent Application. The power system disclosed herein can be used topower such a handle-mounted display.

In certain embodiments, the power system uses an electrically split axleto transmit electrical power from the wheel to other potions of theobject. In the embodiment shown in FIG. 4A, power from the power systemis routed to the PCBA 334 which is connected by wires 378 to the axle234. The axle 234 comprises two electrically conductive (e.g., metal)pieces 234 a and 234 b that are press fit with a first insulating spacer374 a between them to keep the wires 378 from shorting the two pieces234 a, 234 b together. The axle piece 234 b has a step 280 that ensuresproper spacing of the axle pieces 234 a, 234 b and that providespressure on the spacer 374 a to ensure proper insulation between thepieces 234 a, 234 b. A second insulating spacer 374 b prevents the bolt228 from shorting the pieces 234 a, 234 b. The insulating spacers 374 aand 374 b may be made of suitable electrically nonconductive plasticmaterials such as, for example, nylon. A step corresponding to the step280 in the axle piece 234 b may be molded into the second spacer 374 bso that when the bolt 228 is inserted into the axle piece 234 b,friction will cause the second spacer 374 b to be displaced to theposition shown in FIG. 4A, which ensures proper electrical insulation ofthe bolt 228 from both of the axle pieces 234 a and 234 b. In someembodiments, the second spacer 374 b substantially fills the entirelength of the axle 234.

The wires 378 can be soldered to the PCBA 334 and to holes in the axlepieces 234 a, 234 b. Preferably, the surfaces of the two pieces 234 a,234 b that are press fit are shaped (e.g., by keying or by a spline) toprevent the pieces 234 a and 234 b from rotating relative to each other.Although the PCBA 334 is shown as mounted to the axle piece 234 a inFIG. 4A, in other embodiments the PCBA 334 is mounted to an insulatedchassis (e.g., the chassis 312 in FIGS. 3A-3C), which is mounted to theaxle 234.

FIG. 4B is a cross-section view of a portion of the wheel assembly,looking parallel to the ground and perpendicular to the wheel's axis ofrotation. In this embodiment, the caster 240 comprises a non-conductingmaterial, such as a plastic material. The axle 234 engages the retainingclip 225 similarly as described with reference to FIG. 2B. The bolt 228can be secured to the caster 240 by the nut 232 and a (preferablyinsulating) washer 233. The retaining clip 225 is metal with a hardinsulating coating 226. The insulating coating 226 typically needs tosupport only a few volts of breakdown voltage; accordingly, relativelythin layers of coating may be used. In some embodiments, powder coatedsteel or anodized aluminum are used for the retaining clip 225 andinsulating coating 226 The pressure of the flat portion 235 of the axle234 on the retaining clip 225 keeps the retaining clip 225 in electricalcontact with an electrically conductive wire 382 at point 227, therebyproviding an electrical path for the power to flow from the axle 234 tothe wire 382. In some embodiments, the retaining clip 225 includes arecess or slot for the wire 382 to ensure good electrical contact at thepoint 227. The wire 382 can be routed to any other portion of the objectwhere power is desired, for example, by passing the wire 382 throughcart frame tubes. An insulating element 390 attached to or molded intothe caster 240 provides additional mechanical containment of the wire382. The portion of the wire 382 outside the retaining clip 225 iscovered by insulation 386.

The electrically split axle 234 shown in FIGS. 4A and 4B advantageouslyprovides reliable electrical contact between each axle piece 234 a, 234b and the wire 382, while electrically isolating any of the exposedsurfaces of the wheel assembly. In certain embodiments, the electricalisolation provided by the wheel assembly shown in FIGS. 4A and 4B issufficient for currents up to about 100 mA and contact resistances up toseveral tens of milliohms. Additionally, the electrical contact point227 is protected from physical contact with moisture and electrolyticliquids (e.g., salt water), which beneficially avoids galvanic corrosionat the contact point 227, since typically the wire 382 and the axle 234are dissimilar metals. In embodiments suitable for carts, theelectrically split axle 234 is preferably used on a non-swiveling wheel(e.g., a rear shopping cart wheel). Also, in embodiments in which atwo-way communication system and/or a navigation system are disposed inthe wheel, fabricating the caster 240 from nonconductive materialsbeneficially provides from less electromagnetic interference withantennas and magnetic sensors, because there is less conductive (and/orferromagnetic) material close to an antenna.

IV. Power System Control Circuit

The power system includes a control circuit to regulate and controlelectrical power provided by the generator 313. In some embodiments, thecontrol circuit is used to regulate the charging and discharging of theelectric storage device 330. The control circuit may comprise one ormore microcontrollers, which can be configured to perform the controlfunctions discussed herein via hardware, software, and/or firmwareinstructions.

In embodiments of the power system comprising an AC generator 313, it ispreferable, but not necessary, for the control circuit to include arectification circuit that converts the generator's AC current into a DCcurrent. The rectification circuit can include a full-wave rectifierand/or a half-wave rectifier. In some embodiments, the rectificationcircuit comprises a single-phase, diode bridge rectifier havingcapacitive filtering. Further aspects of the rectification circuit arediscussed below.

In embodiments of the electrical storage device 330 using a capacitorbank connected in series, the power system may use one or more chargebalancing techniques to, for example, reduce the likelihood that one (ormore) of the capacitors in the bank exceeds its maximum rated voltage.Since the capacitors in the bank will have a certain amount of variancein their individual capacitances, charge balancing can beneficiallyreduce variances in voltage across the capacitors and variances incharging times. Some embodiments provide charge balancing by using aresistor balancing network (typically in parallel with the capacitors)or a voltage comparator to direct excess charge to ground. In certainpreferred embodiments, the power system control circuit monitors thecharge on the capacitors so as to provide more accurate charge balancingover a wide range of charging conditions.

The power system control circuit may also monitor ambient temperature tocorrect for certain temperature-dependent effects found inultracapacitors. In one of these effects, as the temperature decreases,the ESR of the ultracapacitor increases. Thus, the available energy theultracapacitor can deliver to a high current load (e.g., a wheel lockingmechanism) decreases as the temperature decreases. In another effect, asthe temperature decreases, the voltage to which the ultracapacitor canbe charged without permanently degrading the ultracapacitor'sperformance increases. To achieve a desired level of performance over anoperating temperature range, these effects disadvantageously requireselection of higher capacity ultracapacitors (which are more expensive),because the charging voltage must be calculated based on the highestoperating temperature and the ESR must be based on the lowest operatingtemperature. Accordingly, in some embodiments, the power systemcomprises a temperature sensor, and the control circuit is configured toadjust the charging voltage based on the temperature so as provide moreconsistent performance across a wide temperature range. For example, inan embodiment, the control circuit charges the ultracapacitor to highervoltage at lower temperatures in order to compensate for theultracapacitor's higher internal resistance (ESR) at lower temperatures.It is preferred, but not necessary, for the temperature sensor to bedisposed in proximity to the ultracapacitors so as to measure theirtemperature more accurately. In some embodiments a separate temperaturesensor is utilized. However, in other embodiments, one of the othercomponents in the system may comprise a temperature sensor. For example,in one embodiment, the temperature sensor is a part of a transceiverdisposed in the wheel 212 as part of a communication system.

The control circuit may also be configured to provide separate voltagesto different on- or off-wheel systems. For example, the brake system mayrequire a higher voltage (e.g., 5 V) and may draw more current thanother electronic components (such as microprocessors and transceivers).Additionally, some electronic components preferably need a regulatedvoltage source, while other components (such as a brake motor) do notneed regulated voltage. Accordingly, some embodiments of the controlcircuit provide beneficially provide two or more operating voltages, oneor more of which may be voltage regulated.

Although in the embodiments shown in FIGS. 3A-3E the control circuit isdisposed on the PCBA 334 in the wheel 212, this is not a requirement ofthe power system. In some embodiments, some or all of the controlcircuit is disposed in the wheel 212, in the wheel assembly 210, and/orelsewhere in the object such as, for example, in the frame or in thehandlebars of a cart. Likewise, the electrical storage device 330 can bedisposed in locations outside the wheel 212.

a. Example Power System Control Circuit

As discussed herein, certain preferred embodiments of the wheel powersystem comprise a generator, an electric storage device, and a controlcircuit. The control circuit can be configured to perform a variety offunctions in the power system such as, for example, regulating thecharging and discharging of the electric storage device, chargebalancing a bank of capacitors, regulating temperature dependentcapacitor effects, and providing suitable power to system componentsboth on and off the wheel.

An embodiment of a control circuit 400 a will be discussed withreference to the circuit diagram shown in FIG. 5A. In this circuitdiagram, bold lines indicate electrical paths through which power flowsin the ordinary operation of the power system. Non-bold lines indicateelectrical paths used for monitoring and/or control functions or forexception conditions. Table 1 shows examples of selected components usedin the control circuit 400 a. TABLE 1 Reference Manufacturer Part NumberRelevant Attributes C1, C2 Cooper Bussmann B1010-2R5155 1.5 F.capacitance, 0.3 Ohm ESR D1-D6 ON Semiconductor MBR0520 Low voltage dropat moderate current Q1, Q2 Fairchild FDN337N Low leakage in offSemiconductor state (V_(gs) = 0) U1 Microchip MCP1700 Low dropoutTechnologies voltage, low ground current U2 Atmel Corp. ATMega168V 1.8-Voperation, low power, peripheral circuits (counter, timer, ADC)

As shown in FIG. SA, a generator 404 provides power to the circuit 400a. In this embodiment, the generator 404 comprises an AC generator thatproduces an AC current. The AC current is passed to a rectifier 408,which in this embodiment is a full-wave rectifier. The power from thegenerator 404 is directed to an electrical storage device 410, which inthis preferred embodiment is a capacitor bank comprising ultracapacitorsC1 and C2 connected in series. In other embodiments, the electricalstorage device 410 further comprises a small capacity, lowself-discharge backup battery, which is used to power other electricalcomponents if the ultracapacitors C1 and C2 discharge below a minimumoperating voltage for the other components.

The generator 404 provides unregulated power to various system loadssuch as, for example, a motor drive 420 that actuates a wheel locking orbraking mechanism and other unregulated loads 422. Some of these loads,such as the motor drive 420, require relatively high power but only atintermittent times (e.g., to lock or unlock the wheel). For example,some embodiments of the brake system may require about 4 Joules ofenergy delivered at source voltages greater than about 2 V to perform alock/unlock cycle.

The generator 404 also provides regulated power to other system loadssuch as, for example, a microcontroller U2 and a radio frequency (RF)transceiver 416 (with antenna 418). The generator 404 may also powerother regulated loads such as, for example, a navigation system, acommunication system, a display, and other processors and controllers.The power from the generator 404 is regulated by a voltage regulator U1,which in some embodiments comprises a low dropout (LDO) voltageregulator. In the example circuit 400 a, the voltage regulator U1provides a stable output voltage of 1.8 V, which is suitable for themicrocontroller U2. In other embodiments, the regulated voltage mayrange from about 1.5 V to about 5 V. One embodiment provides a higherregulated voltage by using a boost DC-DC converter.

Various features of the example control circuit 400 a will now bediscussed with reference to FIG. 5A and the example components listed inTABLE 1.

i. Capacitor Bank Charging

The AC output of the generator 404 is rectified by the fall waverectifier 408, which comprises diodes D1-D4. In order for theultracapacitor bank 410 to be charged, the generator's peak voltage mustbe greater than a charging voltage which is equal to twice the voltagedrop across the diode D1 plus the current series voltage on theultracapacitor bank 410 (e.g., C1 and C2). In various embodiments usingSchottky diodes for D1-D4 (e.g., MBR0520 diodes from ON Semiconductor),the forward drop is about 275 mV minimum per diode for any reasonablecharging current (e.g. about 100 ma at room temperature).

Power is available from the generator 404 to power the regulated loads(e.g., microcontroller U2, the RF transceiver 416, and other regulatedloads 412) once the voltage across the ultracapacitor bank 410 exceedsthe minimum operating voltage of the voltage regulator U1 (e.g., about2.3 V for the MCP1700 LDO from Microchip Technologies) plus the forwarddrop of diode D6 at the regulated load current (e.g., about 200 to 250mV depending on load current).

ii. Bootstrap Power

When the capacitor bank 410 (e.g., C1 and C2) has discharged to thepoint where the capacitor bank 410 is below the dropout voltage for theregulator U1, the microcontroller U2 can no longer operate reliably fromthe stored energy in the capacitor bank 410. A bootstrap power path 426through diode D5 provides a secondary, low current, half wave rectifierfor the power output of the generator 404. The generator 404 charges areservoir capacitor C4 relatively quickly. A resistor R1 causes loadcurrent to be pulled preferentially from the full wave rectifier 408(e.g., diodes D1-D4) once the ultracapacitor bank 410 has charged abovethe minimum operating voltage for the voltage regulator U1. Diode D7limits the voltage through the bootstrap power path 426 to the maximumallowable input voltage of the voltage regulator U1 (e.g. 6.0 V for theMCP 1700).

In a representative embodiment, a minimum output frequency of thegenerator 404 is about 100 Hz, and the mean load current of themicrocontroller U2 plus the RF transceiver 416 is on the order of 2milliamps. Accordingly, the charge which the reservoir capacitor C4 mustdeliver across one 10 millisecond cycle of the generator 404 is no morethan about 20 microCoulombs. A 50 μF capacitor may be used for thereservoir capacitor C4 and will deliver about 20 microCoulombs of chargewith a voltage drop of about 0.4 V. Therefore, in such an embodiment,the bootstrap charging voltage for the reservoir capacitor C4 need onlybe about equal to the minimum charging voltage of the voltage regulatorU1 plus the voltage drop across the reservoir capacitor C4. Thebootstrap charging voltage is about 2.7 V if the voltage regulator U1 isan MCP1700 (Microchip Technologies). The bootstrap charge on thereservoir capacitor C4 is sufficiently low that even a relatively lowpower generator 404 will be able to charge the reservoir capacitor C4 tothe minimum charging voltage of the voltage regulator U1 within a fewseconds of rotational motion. Accordingly, use of the bootstrap powerpath and the reservoir capacitor C4 advantageously permits regulatedloads to operate within a few seconds of motion of the object, even ifthe ultracapacitor bank 410 is fully discharged.

iii. Charge Balancing of the Capacitor Bank

As discussed above, it is preferable, but not necessary, to chargebalance two or more capacitors connected in series, because thecapacitors (e.g., C1 and C2) will have some variance in theircapacitance. For example, two nominally identical ultracapacitors candiffer in their actual capacitance by a factor of about two. The CooperBussmann B1010-2R5155 EDLC ultracapacitor has a manufacturing toleranceof −20% to +80% based on the nominal 1.5 F capacitance value. Moreover,an ultracapacitor can be damaged if its maximum charge voltage isexceeded. Since the amount of charge carried on two series capacitors isthe same, the maximum charge voltage will be limited by the need toavoid overcharging the lowest capacitance ultracapacitor, if there is nomeans of steering charge to or from the individual ultracapacitors ofthe bank

For example, in a two-capacitor bank, if the maximum charge voltage is2.5 V, and one nominally 1.5 F ultracapacitor has a capacitance that is10% low, e.g., 1.35 F, while the other has a capacitance that is 70%high, e.g., 2.55 F, then 3.375 Coulombs is needed to charge the 1.35 Fcapacitor to 2.5 V. However, this amount of charge will charge thelarger capacity ultracapacitor to only 1.32 V (e.g., 3.375 C/2.55 F).The total energy stored in the capacitor bank is the sum of the energiesof the individual capacitors [e.g., ½ C V²], namely, ½(1.35 F*(2.5V)²+2.55 F*(1.32 V)²) or 6.4 Joules. Fully charging each ultracapacitorto 2.5 V stores ½*(1.35 F*(2.5 V)²+2.55 F*(2.5 V)²) or 12.2 Joules,almost twice the energy.

The charge balancing circuit 430 comprises one transistor for eachultracapacitor in the capacitor bank 410. For example, transistors Q1and Q2 perform charge balancing between the ultracapacitors C1 and C2.If the ultracapacitors C1 and C2 are fully charged, each of thetransistors Q1 and Q2 can be made conducting to avoid overcharging theultracapacitors C1 and C2. In one preferred embodiment, the transistorsQ1 and Q2 are N channel enhancement mode FETs such as, e.g., an FDN337NFET from Fairchild Semiconductor.

In the embodiment shown in FIG. 5A, charge balancing is monitored andperformed by the microcontroller U2, which measures the voltages on theultracapacitors C1 and C2. The voltage on ultracapacitor C2 isdetermined by performing an analog-to-digital conversion on the outputof voltage divider VD3, while the output of voltage divider VD2 providesa measurement of the combined voltages on the ultracapacitors C1 and C2.Accordingly, the voltage on the ultracapacitor C1 can be found bysubtraction. If the voltage on the ultracapacitor C1 is higher than thevoltage on the ultracapacitor C2, the microcontroller U2 puts thetransistor Q1 into conduction until the voltages equalize, and similarlyif the voltage on the ultracapacitor C2 is higher than the voltage onthe ultracapacitor C1. In this embodiment, the transistor Q1's gatedrive is pulled up through a resistor R2 and pulled down via an opencollector driver included in or attached to the microcontroller U2,because the microcontroller U2 can only drive an output high to theregulated positive rail Vcc (e.g., 1.8V for the ATMega 168V) rail. Toput the transistor Q1 into conduction requires a positive Vgs across thetransistor Q1 (e.g., >0.7 V for the FDN337N FET). If the ultracapacitorC2 is nearly fully charged, this voltage is above about 3.0 V.

iv. Rotation Monitor and Voltage Measurement Functions

In certain embodiments, the object includes a navigation system thatdetermines the position of the object. For example, in certain preferredembodiments, the position of the object is tracked via a dead reckoningmethod that measures the object's heading and the distance traveled byobject. In certain such embodiments, the distance traveled by the objectis determined by measuring the amount of wheel rotation (e.g., under theassumption that the wheel does not slide, slip, or skid). Furtherdetails of a suitable navigation system are discussed in the NavigationPatent Application.

In certain embodiments, the generator 404 can act as a wheel rotationsensor for the navigation system, because the generator voltage varieswith a frequency that is proportional to the wheel rotation frequency.In the embodiment of the generator 313 shown in FIG. 3D, the frequencyof the generator voltage equals the wheel rotation frequency multipliedby the gear ratio between the generator drive gear ring 314 and thepinion gear 326. Accordingly, in some preferred embodiments, the voltageproduced by the generator 404 is monitored and used as a wheel rotationcounter. As shown in FIG. 5A, the rotation counter comprises a half waverectifier, e.g., diode D8, which is voltage limited by a diode D9, andwhich provides a “rotation” input to the microcontroller U2. Therotation input can be counted by a counter circuit on themicrocontroller U2 to determine the number of wheel rotations and thus,the distance traveled by the object. By suitably providing an elapsedtime circuit (e.g., a clock on the microcontroller U2), the object'sforward speed can be estimated from the number of wheel rotations andthe elapsed time.

The diode D8 also provides an instantaneous measurement of the generatorvoltage during a positive half-cycle. The voltage measurement is reducedby the voltage divider VD1 to a suitable value for the range of an ADCon the microcontroller U2. A diode D10 also limits the voltage into theADC in cases of extremely high generator voltage.

v. Wheel Brake Mechanism Drive

Power from the ultracapacitor bank 410 can be used to operate the motordrive 420 for the braking mechanism until the voltage on theultracapacitor bank 410 is less than the minimum voltage needed togenerate sufficient torque to disengage the brake. The minimum voltagedepends on the details of the braking mechanism and the motor thatdrives the braking mechanism. In the embodiments shown in FIGS. 3A-3E,the minimum operating voltage is about 2.0 V.

The two-ultracapacitor bank 410 described herein has a worst case DC ESRafter aging of about 1.5 Ohms and has a locking stall current on theorder of 500 ma at 3.0 V. The voltage drop across the ultracapacitorbank 410 at locking stall is approximately 0.75 V in some embodiments. Abuffer capacitor C3, having a low ESR, provides some buffering for highcurrent transient loads such as, for example, the stall current of themotor drive 420 and the inductive kick from commutator switches in themotor drive 420.

It is preferable, but not necessary, for the brake mechanism's powersource to be high compliance (e.g., having a low apparent sourceresistance). In the example circuit 400 a shown in FIG. 5A, power is fedto the braking motor drive 420 (which may include a MOSFET H-bridge)directly from the ultracapacitor bank 410 in parallel with the buffercapacitor C3 but with no diodes in the path. Such a circuit provideshigh compliance power subject only to inherent limitations of thespecific ultracapacitors chosen for the bank 410. If higher complianceis needed, then each series ultracapacitor in the ultracapacitor bank410 can be replaced by two or more lower capacity ultracapacitors toreduce the circuit ESR. For example, two 300 milliohm ESRultracapacitors connected in parallel have a circuit ESR of 150milliohms. In some embodiments, a high-capacity high-ESR ultracapacitoris connected in parallel with a low-capacity, low-ESR ultracapacitor toform a high-capacity, low-ESR combination. For example, in oneembodiment the high-capacity high-ESR ultracapacitor comprises a CooperBussmann B1010-2R5155 ultracapacitor, while the low-capacity, low-ESRultracapacitor comprises a Cooper Bussmann A0820-2R5474 0.47 F, 150milliohm ESR ultracapacitor.

vi. Decision Logic for Extended Time in a Wheel Lock State

In some situations, a wheel's brake mechanism is activated, and thewheel remains in the locked state for an extended period of time.Typically, energy stored in the ultracapacitor bank 410 is later used tounlock the wheel. However, the energy stored in the ultracapacitor bank410 decays with time, because the ultracapacitors self-discharge. If thewheel is locked for too long a time period, the energy in theultracapacitor bank 410 will be too small to unlock the wheel. At thispoint, the wheel will remain locked until commanded to unlock (e.g., byan authorized person who has a device that can issue a suitable unlockcommand). The energy to perform this unlock will have to come from anenergy source other than the ultracapacitor bank 410. For example, incertain embodiments, a backup battery may contain sufficient energy tounlock the wheel. However, in other embodiments, the wheel will have tobe supplied with power from an external source.

The ultracapacitor bank discharge time for the example embodimentdepicted in FIG. 5A and TABLE 1 is typically a few days. However, thedischarge time may be shorter if the ultracapacitor bank 410 was notfully charged before the wheel locked.

Certain embodiments of the control circuit 400 a beneficially avoidleaving a wheel in an extended lock state, by unlocking the wheel at apoint where the ultracapacitor bank 410 has just enough energy toperform a wheel unlock cycle. In such embodiments, the microcontrollerU2 periodically monitors the charge state of the ultracapacitor bank 410to determine whether the ultracapacitors have reached this point. Afterunlocking the wheel, the wheel can rotate freely, and the object (towhich the wheel is attached) can be moved.

In certain situations, it may be undesirable to leave the wheelunlocked, because the object can be stolen. Accordingly, in someembodiments, the microcontroller U2 can be configured to implement thefollowing decision logic in this situation. The decision logic dependson whether or not the wheel includes a backup power source (e.g., abackup battery).

In the case where the wheel does not have a backup power source, if thewheel begins rotating again, the microcontroller U2 waits until theultracapacitor bank 410 has charged sufficiently to perform a completelock/unlock cycle. The microcontroller U2 then signals the wheel to lockagain. The rationale behind this decision logic is that the wheelinitially locked correctly (e.g., the object was being stolen), and theobject was then abandoned after the wheel locked. By subsequentlyunlocking the wheel, the decision logic acts under the assumption thatunlocking the wheel when the ultracapacitor bank 410 has just enoughenergy left to unlock the wheel is unlikely to result in the objectbeing moved again. Alternatively, if the cart does move after themicrocontroller U2 unlocks the wheel, the rationale assumes thatpermitting the object to move far enough to recharge the ultracapacitorbank 410 will not significantly affect the object's chance of beingultimately recovered.

In an alternate embodiment of the decision logic, the wheel isimmediately locked by the backup power supply if the wheel begins torotate again. In this alternate embodiment, the rationale is thatsubsequent motion of the wheel is likely to lead to the loss of theobject. In certain embodiments, different choices for the decision logiccan be made when the control circuit 400 a is initialized, for example,by storing a suitable flag in nonvolatile memory (e.g., EEPROM).

A further embodiment uses a low-current-capacity backup battery that isnot capable of unlocking the wheel. In such an embodiment, the wheel isunlocked when the ultracapacitor bank 410 discharges to the point whereit contains the minimum energy to reliably perform the unlock cycle. Ifthe wheel is subsequently moved by an unauthorized person or in anunauthorized way, the microcontroller U2 waits until the ultracapacitorbank 410 is sufficiently charged so as to perform a complete lock/unlockcycle. The microcontroller U2 then signals the wheel to lock again.Certain embodiments of the wheel locking mechanism require a peakcurrent of about 500 mA to perform an unlock cycle. Many commerciallyavailable batteries utilize battery chemistries that have a sufficientlyhigh internal resistance that the current they produce is insufficientto lock or unlock various preferred embodiments of the brake mechanism.

vii. Auxiliary Backup Battery

In some embodiments, the wheel comprises an auxiliary backup batterythat acts as a source of power when the energy in the ultracapacitorbank is low. The backup battery typically comprises a non-rechargeablebattery such as an alkaline or primary lithium battery, althoughrechargeable batteries such as lithium ion batteries may be used inother embodiments. A float charge voltage is applied across thenon-rechargeable battery in certain embodiments, which may reduce theself-discharge rate of the battery.

FIG. 5B is a circuit diagram showing an embodiment of a power systemcontrol circuit 400 b including a backup battery system 450 and anoptional charging circuit 460 (used to recharge rechargeable backupbatteries). The control circuit 400 b is configured to provide power tounregulated loads 420 and 422 and the regulated loads U2, 412, and 416.

After a discharge time, an initially fully charged capacitor bank 410will self-discharge to a point where the voltage is not high enough topower the voltage regulator U1. The microcontroller U2, whichperiodically monitors the voltage on the ultracapacitors C1 and C2, putsa transistor Q3 into conduction (e.g., the gate of the transistor Q3 ispulled up through a resistor R4 so that the transistor Q3 is fullysaturated). When the transistor Q3 begins conducting, the backup batterywill start charging the ultracapacitors C1 and C2, with a currentlimited by the ESR of the ultracapacitors C1 and C2. The microcontrollerU2 then turns off the transistor Q3. The regulated loads then arepowered by the energy transferred from the backup battery to theultracapacitor bank 410, until the bank 410 again dischargessufficiently, at which point this cycle repeats.

If a wheel lock condition is detected and there is not enough energy inthe ultracapacitor bank 410 to perform the lock, the microcontroller U2puts the transistor Q3 into conduction so as to add enough charge to theultracapacitor bank 410 to perform the lock, after which themicrocontroller 410 turns off the transistor Q3. Similar decision logicapplies if there is insufficient energy to perform an unlock.

In certain embodiments, the backup battery runs only the microcontrollerU2 and the other regulated loads 412 and 416. In such embodiments, thecontrol circuit 400 b is modified by connecting the output of thetransistor Q3 to the cathode side of the diode D6 (rather than the anodeside as shown in FIG. 5B). The transistor Q3 is made conducting wheneverthe voltage of the ultracapacitor bank 410 is below the minimum neededto run the voltage regulator U1. In these embodiments, the diode D6 isincluded in the control circuit, regardless of whether the bootstrappower path 426 is used. Some embodiments beneficially use the backupbattery system 450 instead of the bootstrap power circuit (e.g., theportion of the circuit including the diodes D5, D6, D7, the capacitorC4, and the resistor R1).

viii. Powering an Ultracapacitor Bank

A test was performed to measure properties of one embodiment of thepower system. The ultracapacitor bank comprised three Cooper BussmannPowerStor B0830-2R5475 EDLC ultracapacitors (1.6 F and 0.45 Ohm nominalESR) in series. The ultracapacitor bank had a maximum working voltage of7.5 V. Diodes D1-D4 in the full wave rectifier were BAT54T Schottkybarrier diodes (Diodes Inc, Westlake Village, Calif.), which were chosenfor their low forward drop at low currents. A Zener shunt regulatorLM432 (National Semiconductor Corp., Santa Clara, Calif.) was connectedin parallel with the ultracapacitor bank to limit the voltage dropacross the bank to be about 7.2 V. TABLE 2 estimated average poweraverage worst case power time test simulation to ultracap currentdiode + ESR generated (s) voltage (V) voltage (V) (mW) (mA) drop (V)(mW) 10 1 1.2 78 157 1.5 315 17 1.5 1.8 140 112 1.4 291 24 2 2.2 196 1121.3 345 32 2.5 2.7 220 98 1.3 352 42 3 3.2 215 78 1.2 312 51 3.5 3.6 28387 1.2 391 61 4 4.0 294 78 1.2 391 72 4.5 4.4 303 71 1.2 390 85 5 4.9286 60 1.0 348 100 5.5 5.4 274 52 1.1 330 114 6 5.8 322 56 1.0 378 1326.5 6.3 272 44 1.0 315 152 7 6.8 264 39 0.9 301 mean power 253 estimated340 harvested mean power (mW) generated (mW)

TABLE 2 shows the results of an experiment on the test embodiment powersystem. The generator (shown in FIG. 3D) was driven by a mechanicaldrill motor, thereby providing a sinusoidal generator output with anapproximate frequency of 330 Hz and a wheel rotation of approximately165 RPM. The voltage across the ultracapacitor bank was recorded as afunction of time while the generator was in motion. In TABLE 2, resultsin the column labeled “Worst case diode drop+ESR drop (V)” wereestimated from the diode datasheet at twice the average current for eachvoltage step (note that there are two diode drops, e.g., D1 and D4, forthe positive generator phase). Also, the ESR was taken from theultracapacitor datasheet (and may be somewhat conservative).

TABLE 2 also shows the results of a discrete time simulation whichtreated the generator as a constant power source regardless of loadcurrent. In this simulation, it was assumed that the generator producedan instantaneous power of (π/2)·0.31(mW)·sin ωt and produced a maximumvoltage of 13(V)—sin ωt. The discrete time simulation modeled the diodevoltage drop across the full wave rectifier according to an exponentialfit, which had an accuracy of about 0.05V over the voltage ranges in thetest. TABLE 2 shows that the results of the discrete time simulation areclose to the test results, with the simulation results being slightlymore optimistic at low ultracapacitor charge levels and slightly morepessimistic at higher charge levels

The results in TABLE 2 show that one embodiment of the power systemoperating at speeds typical of a cart propelled by human locomotion isable to produce an average usable power of about 250 mW. The totalenergy that can be stored in an ultracapacitor bank comprising twoCooper Bussmann B1010-2R5155 EDLC's nominally rated at 1.5 F and havinga working voltage of 5.0 V is 9.4 Joules, which can be harvested in lessthan about 40 seconds of use with this embodiment. At a walking speed ofabout 2 ft/sec, the object is moved through a distance of about 80 feetto fully charge the ultracapacitor bank. Accordingly, an ultracapacitorbank disposed in a wheeled object (e.g., a shopping cart) is likely tobe rapidly charged by certain embodiments of the generator disclosedherein.

In some embodiments, the ultracapacitor bank can hold its charge forseveral days or longer, which is typically much longer than the timeintervals between when the object is moved (and the generator isoperated). Thus, for example, in a retail store environment theultracapacitor bank will likely remain fully charged with even moderateand intermittent use by customers. In the event that a cart is removedfrom a confinement area surrounding the retail store, the ultracapacitorbank will contain sufficient stored electrical energy to actuate alocking mechanism to inhibit theft of the cart.

Although the invention(s) have been described in terms of certainpreferred embodiments and certain preferred uses, other embodiments andother uses that are apparent to those of ordinary skill in the art,including embodiments and uses which do not provide all of the featuresand advantages set forth herein, are also within the scope of theinvention(s). Accordingly, the scope of the invention(s) is defined bythe claims that follow and their obvious modifications and equivalents.

1. A power generator configured for use on a wheeled vehicle, the powergenerator comprising: a housing comprising windings; a magnetizedelement disposed within the housing and operable to rotate about anaxis; and a drive mechanism configured to cause the magnetized elementto rotate in response to rotation of the wheel; wherein the rotation ofthe magnetized element produces electrical power in the windings so asto enable the generator to supply electrical power; and wherein thehousing, the magnetized element, and the drive mechanism are disposedwithin a wheel of the vehicle.
 2. The power generator of claim 1,wherein the power generator is configured to supply power to anelectronic component located on the vehicle.
 3. The power generator ofclaim 2, wherein the electronic component is a two-way communicationsystem.
 4. The power generator of claim 2, wherein the electroniccomponent is a video display.
 5. The power generator of claim 2, whereinthe electronic component is an audio speaker.
 6. The power generator ofclaim 2, wherein the electronic component is a navigation system.
 7. Thepower generator of claim 2, wherein the electronic component isconfigured to inhibit movement of the vehicle.
 8. The power generator ofclaim 1, further comprising a stator located substantially on the axisand wherein the magnetized element comprises a rotor.
 9. The powergenerator of claim 1, wherein the power generator is configured tosupply power to an energy reservoir also located on said vehicle. 10.The power generator of claim 9, wherein the energy reservoir is locatedin the wheel.
 11. The power generator of claim 9, wherein the energyreservoir comprises capacitive storage devices.
 12. The power generatorof claim 11, further comprising a battery adapted to store electricalenergy.
 13. The power generator of claim 12, wherein the batterycomprises a rechargeable battery.
 14. The power generator of claim 12,wherein the battery is configured to provide supplemental power.
 15. Thepower generator of claim 11, wherein the capacitive storage devicescomprise ultracapacitors.
 16. The power generator of claim 15, whereinthe ultracapacitors comprise at least two charge balancedultracapacitors connected in a series configuration.
 17. The powergenerator of claim 16, wherein the generator is configured to betemperature sensitive and to adjust the amount of energy produced forstorage in the ultracapacitors in response to temperature.
 18. The powergenerator of claim 1, further configured to power a system configured toinhibit motion of the vehicle.
 19. The power generator of claim 1,further configured to power a wheel braking system control circuit. 20.The power generator of claim 19, wherein the wheel braking systemcontrol circuit comprises a power management system for moving a brakefrom a first state to a second state and maintaining the brake in thesecond state until occurrence of a predetermined condition.
 21. Thepower generator of claim 20, wherein the predetermined condition is anexternally produced signal requesting a change of state of the brake.22. The power generator of claim 20, wherein the predetermined conditionis reflective of energy required for producing a change of state of thebrake.
 23. A power management system configured for use on a moveableobject having a wheel, the power management system comprising: agenerator operative in response to movement of the object; a capacitiveenergy storage reservoir connected to the generator; and an electroniccomponent configured to control power usage from the reservoir basedupon a level of energy in said reservoir; wherein the generator, thecapacitive energy storage reservoir, and the electronic component aredisposed within the wheel.
 24. The power management system of claim 23,wherein the storage reservoir comprises at least one ultracapacitor. 25.The power management system of claim 23, wherein the electroniccomponent regulates an amount of charge in the capacitive energy storagereservoir.
 26. The power management system of claim 23, wherein thestorage reservoir comprises a battery.
 27. The power management systemof claim 23, wherein the electronic component provides a regulatedvoltage.
 28. A braking system for a wheel of an object, the brakingsystem comprising: a brake mechanism associated with the wheel so as tobrake or release the rotation of the wheel; a controller associated withthe brake mechanism and configured to cause the brake mechanism to brakeor release wheel rotation; a power storage device connected to supplypower to the brake mechanism in response to signals from the controller;and a generator on the wheel and configured to provide power to thestorage device, said generator operative in response to rotation of thewheel.
 29. The braking system of claim 28, wherein the object is a cart.30. The braking system of claim 29, wherein the cart is a shopping cart.31. The braking system of claim 29, wherein the cart is configured tomove in response to manually applied force.
 32. The braking system ofclaim 28, wherein the power storage device comprises at least oneultracapacitor.
 33. The braking system of claim 28, wherein thecontroller is configured to cause the brake mechanism to brake orrelease in response to occurrence of predetermined criteria.
 34. Thebraking system of claim 33, wherein the criteria includes a level ofpower in the energy storage reservoir which at a predeterminedthreshold.
 35. A method of managing power in a braking system of anobject having a wheel, the method comprising: generating power inresponse to rotation of the wheel; storing said generated power in acapacitive storage reservoir; applying braking force to the wheel usingpower from the reservoir; monitoring a level of power in the reservoir;and releasing the braking force when the monitored level is in apredetermined condition.
 36. The method of claim 32, the method furthercomprising: providing supplemental power in response to a definedcondition so as to apply a braking force.
 37. The method of claim 36,wherein the defined condition relates to a second level of power in thereservoir.
 38. A power generation system configured for use on a vehiclehaving a wheel, the power generation system comprising: a generatordisposed within the wheel, the generator configured to convert rotationof the wheel into electrical energy; an electrical energy storage deviceelectrically coupled to the generator and configured to store a portionof the electrical energy, the storage device disposed in the vehicle;and a power management system electrically coupled to the generator andthe storage device, the power management system configured to monitor alevel of electrical energy in the storage device.
 39. The powergeneration system of claim 38, wherein the vehicle is a cart.
 40. Thepower generation system of claim 39, wherein the cart is a shoppingcart.
 41. The power generation system of claim 38, wherein the electricstorage device comprises at least one ultracapacitor.
 42. The powergeneration system of claim 38, wherein the electric storage device isdisposed within the wheel.
 43. The power generation system of claim 38,wherein the power generation system is configured to provide electricalenergy to a component disposed in or on the vehicle.
 44. The powergeneration system of claim 43, wherein the component is configured toinhibit motion of the vehicle.
 45. The power generation system of claim43, wherein the component is disposed within the wheel.
 46. The powergeneration system of claim 45 wherein the component is a wheel brakemechanism movable between a locked position, wherein the rotation of thewheel is substantially inhibited, and an unlocked position, wherein therotation of the wheel is substantially permitted.
 47. The powergeneration system of claim 46, wherein the power management system isfurther configured to signal the wheel brake mechanism to move betweenthe locked position and the unlocked position if the electrical energystored in the electric storage device reaches a threshold value.
 48. Thepower generation system of claim 47, wherein the threshold value isrelated to an amount of electrical energy used to move the wheel brakemechanism from the locked position to the unlocked position.
 49. A powersystem in an object having a wheel, the power system comprising: meansfor generating electrical power from rotation of the wheel; means forstoring electrical power; and means for charging the storage means byusing power from the generating means; wherein the generating means, thestoring means, and the charging means are disposed within the wheel. 50.The power system of claim 49, wherein the means for storing electricalpower comprises at least one ultracapacitor.
 51. The power system ofclaim 49, wherein the means for storing electrical power comprises arechargeable battery.
 52. The power system of claim 49, furthercomprising means for distributing the electrical power from thegenerating means or the storing means to an electrical component. 53.The power system of claim 52, wherein the electrical component is atwo-way communication system.
 54. The power system of claim 52, whereinthe electrical component is a navigation system.
 55. The power system ofclaim 52, wherein the electrical component is a display device.
 56. Thepower system of claim 52, wherein the electrical component is a brakesystem.
 57. The power system of claim 52, wherein the electricalcomponent is configured to inhibit motion of the object.
 58. The powersystem of claim 52, wherein the electrical component is a wheel steeringsystem.